1. Field of the Invention
The invention relates in general to an electrostatic discharge protection apparatus, and more particularly to an electrostatic discharge protection apparatus of an optical disk drive for preventing damage to delicate electronic components from electrostatic discharge.
2. Description of the Related Art
Electrostatic charges accumulate on the surface of human body and can be as high as several thousands of voltages. When a user touches an electronic product by hand, electrostatic charges suddenly flow to the electronic product. As a result, IC chips on a circuit board inside the electronic product are damaged by electrostatic discharge (ESD), which causes malfunction of the electronic product.
As shown in FIG. 1, a metal plate 2 is disposed on the back of the panel 3 in a conventional optical disk drive 1 for preventing the damage caused by electrostatic discharge. The metal plate 2 closely surrounds an eject button 4 on a panel 3. The panel 3 is disposed on the front of a tray 5, so that the metal plate 2 contacts the front side of a metal base plate (not shown in FIG. 1) under the tray 5. The metal base plate contacts a spindle motor 6 disposed on the tray 5. A cable 7 providing electricity and signals connects the spindle motor 6 with a main board 8. The main board 8 is disposed on the back of a casing 9 of the optical disk drive 1 and contacts the casing 9. The main board 8 and the casing 9 provide a grounding path for dissipating electrostatic charges. A signal line of the cable 7 is grounded through the main board 8 and the casing 9. When the eject bottom 4 is pushed by a user manually, electrostatic charges from the human body is directed by the metal plate 2 toward the spindle motor 6 through the base plate. Then, electrostatic charges are dissipated to the ground through the signal line 7, the main board 8 and the casing 9. Therefore, electrostatic charges do not flow to electronic components on the tray 5, and the delicate electronic components are not damaged by electrostatic charges.
However, the signal line of the cable 7 is a flexible printed circuit board (PCB) cable, and the diameter of the signal line is limited. Generally, electrostatic charges can be dissipated through the signal line, but electrostatic charges with thousands of voltages can not be dissipated through the signal line in time due to the relatively small diameter of the signal line. As a result, electrostatic charges accumulate on the metal plate 2 and the base plate, which increases the possibility of damaging the delicate electronic components by electrostatic charges. Moreover, for reducing the cost and weight of the optical disk drive, not only is the tray 5 integrally formed by plastic, but also a frame of a traverse 10 disposed on the tray 5 is formed integrally by plastic. Therefore, the metal components on the tray 5 are not electrically connected with each other, and electrostatic charge accumulation can not be dissipated. Especially when the tray 5 is ejected from the optical disk drive, an object with electrostatic charges may also contact areas other than the eject bottom 4. Thus, the possibility of the delicate electronic components being damaged by electrostatic charges is increased enormously. Therefore, there are still issues regarding electrostatic discharge protection of optical disk drives that need to be solved.